Cryphonectriaceae on Myrtales in China: phylogeny, host range, and pathogenicity

Abstract

Plantation-grown Eucalyptus (Myrtaceae) and other trees residing in the Myrtales have been widely planted in southern China. These fungal pathogens include species of Cryphonectriaceae that are well-known to cause stem and branch canker disease on Myrtales trees. During recent disease surveys in southern China, sporocarps with typical characteristics of Cryphonectriaceae were observed on the surfaces of cankers on the stems and branches of Myrtales trees. In this study, a total of 164 Cryphonectriaceae isolates were identified based on comparisons of DNA sequences of the partial conserved nuclear large subunit (LSU) ribosomal DNA, internal transcribed spacer (ITS) regions including the 5.8S gene of the ribosomal DNA operon, two regions of the β-tubulin (tub2/tub1) gene, and the translation elongation factor 1-alpha (tef1) gene region, as well as their morphological characteristics. The results showed that eight species reside in four genera of Cryphonectriaceae occurring on the genera Eucalyptus, Melastoma (Melastomataceae), Psidium (Myrtaceae), Syzygium (Myrtaceae), and Terminalia (Combretaceae) in Myrtales. These fungal species include Chrysoporthe deuterocubensis, Celoporthe syzygii, Cel. eucalypti, Cel. guangdongensis, Cel. cerciana, a new genus and two new species, as well as one new species of Aurifilum. These new taxa are hereby described as Parvosmorbus gen. nov., Par. eucalypti sp. nov., Par. guangdongensis sp. nov., and Aurifilum terminali sp. nov. Pathogenicity tests showed that the eight species of Cryphonectriaceae are pathogenic to two Eucalyptus hybrid seedlings, Melastoma sanguineum branches, and Psidium guajava and Syzygium jambos seedlings. The overall data showed that Chr. deuterocubensis is the most aggressive, followed by Par. eucalypti. Significant differences in tolerance were observed between the two tested Eucalyptus hybrid genotypes, suggesting that disease-tolerant genotypes can be selected for disease management in the Eucalyptus industry.

Cryphonectriaceae associated with rust-infected Syzygium jambos in Hawaii

“…This fungus, originally known as Chr. cubensis and later recognised as distinct from that species (Van der Merwe et al 2010), is well-known from many south-eastern Asian countries where it is believed to have originated (Zhou et al 2008;Gryzenhout et al 2009;Chen et al 2010;Van der Merwe et al 2010;Wang et al 2020). It exclusively infects trees in the Myrtaceae and is an important pathogen of Eucalyptus outside the native range of this tree (Gryzenhout et al 2009;Van der Merwe et al 2010).…”

“…They occur on trees and shrubs in various parts of the world and include saprophytes, facultative parasites and important pathogens of woody plants (Gryzenhout et al 2009). Pathogens in the family reside mainly in the genera Cryphonectria and Chrysoporthe and include important agents of tree disease, both in natural forest ecosystems, as well as in intensively-managed plantations (Wingfield 2003;Gryzenhout et al 2009;Wang et al 2020). These fungi generally have yellow to orange or brown stromata and these structures turn purple in 3% potassium hydroxide (KOH) or yellow in lactic acid (Gryzenhout et al 2006c(Gryzenhout et al , 2009Jiang et al 2020).…”

Figure 1 from: Roux J, Kamgan Nkuekam G, Marincowitz S, van der Merwe NA, Uchida J, Wingfield MJ, Chen SF (2020) Cryphonectriaceae associated with rust-infected Syzygium jambos in Hawaii. MycoKeys 76: 49-79. https://doi.org/10.3897/mycokeys.76.58406

“…& M.J. Wingf., native to Southeast Asia and causal agent of a canker disease of Eucalyptus species in Africa, Australia, China and Hawaii (Davison and Coates 1991;Roux et al 2005;Nakabonge et al 2006;Zhou et al 2008;Chen et al 2010;Van der Merwe et al 2010;Wang et al 2020); and Chrysoporthe austroafricana Gryzenh. & M.J.…”

Figure 2 from: Roux J, Kamgan Nkuekam G, Marincowitz S, van der Merwe NA, Uchida J, Wingfield MJ, Chen SF (2020) Cryphonectriaceae associated with rust-infected Syzygium jambos in Hawaii. MycoKeys 76: 49-79. https://doi.org/10.3897/mycokeys.76.58406

“…The Cryphonectriaceae infect trees and shrubs residing in more than 100 species in at least 26 families and 16 orders of plants worldwide (Gryzenhout et al 2009;Jiang et al 2020;Wang et al 2020). The chestnut blight pathogen, Cryphonectria parasitica (Murrill) M.E.…”